Delphi detecting unicode

I need to be able to detect when a unicode character is being presented during the keydown event. I'm using Delphi 7 which doesn't have the best unicode support. What's happening is I'm reading in a PDF417 barcode... and the scanner is pushing characters to the edit field. I need to intercept the heart code (alt-2) and the smiley face code 02 and convert them to empty strings or a standard ASCII character. All I need is the two or three lines of code that will do this.